A power converter includes a rectangular casing that houses a semiconductor module, and bosses extending outward from three of four side walls of the casing excluding a rear side wall. The bosses include a first boss provided on a first side wall facing frontward, a second boss provided on a second side wall facing in a width direction of the mobile object orthogonal to an up-down direction and a front-rear direction, and a third boss provided on a third side wall opposite to the second side wall. The third boss is smaller in cross-sectional area than the second boss.